1. Field of the Invention
The present invention relates to a semiconductor laser.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2008-066318 discloses a wavelength tunable semiconductor laser. This wavelength tunable semiconductor laser includes a plurality of ring resonators having mutually different free spectral ranges (FSRs), and a gain region optically coupled to the plurality of ring resonators. More specifically, both ends of the gain region are respectively optically coupled to input ports of the individual ring resonators. Output ports of the ring resonators are optically coupled to a light emission end facet. The wavelength tunable semiconductor laser described in Japanese Unexamined Patent Application Publication No. 2008-066318 performs wavelength tuning by using vernier effect provided by the plurality of ring resonators having the mutually different FSRs.